KR20130005527A - Realtime transcoding device for progressive downloading of which meta data and media data saperated - Google Patents

Abstract

PURPOSE: A real time trans coding device to progressively download the multimedia contents in a file format with the separated metadata and media data aids the progressive download of a user end terminal by coding multimedia contents stored in a storage device in a server with the use of a trans coder in real time through the control of a two staged bit rate in between screens or in the screen. CONSTITUTION: A metadata reprocessing unit(20) reprocesses a metadata(100) inputted. A one-step bit rate controller(22) supplies the right metadata generation by using an inter-screen correlation and the proper inter-screen bit rate to the metadata reprocessing unit. A decoding unit(24) decodes some part of whole part of a screen data(104) received from a media data(102). An encoding unit(26) encodes the decoded data in a desired codec. A two-step bit rate controller provides the optimal bit rate through an intra-screen correlation and the reattempt of encoding in the encoding unit. [Reference numerals] (10) Media data; (100) Metadata; (104) Screen data; (2) MP4 file converting unit; (20) Metadata reprocessing unit; (22) One-step bit rate controller; (24) Decoding unit; (26) Encoding unit; (28) Two-step bit rate controller; (3) Network; (AA) MP4 file format; (BB) Repeated attempt; (CC) Compression rate; (DD) Real-time transmission

Description

Real-time transcoding device for progressive downloading of which meta data and media data saperated}

The present invention relates to a real-time transcoding device that is installed on the server side for progressive download of multimedia content from a user terminal. More specifically, the present invention relates to metadata such as MP4, skm, k3g, 3gp, and 3gp2 file formats. The present invention relates to a real-time transcoding apparatus installed on a server side to support progressive download of multimedia contents in a file format in which media data is separated, while maintaining optimal image quality in a user terminal.

Advances in multimedia systems have had a significant impact on image compression. In particular, as the number of communication environments, video compression schemes, and various user devices have increased, solving the compatibility problem between different systems and communication environments has become an important element of the multimedia service. Accordingly, devices such as gateways and servers need to transmit content in a format suitable for network bandwidth and user devices in order to provide seamless service to users. In the case of limited network bandwidth such as a wireless environment, it is difficult to transmit high resolution / high definition video data, and the transmission method also needs to be converted into a suitable form because there are differences depending on user devices.

Progressive download, one of several transfer methods, plays a video file as soon as it arrives as it arrives from the server to the user's device, which can reduce unnecessary network wastage and playback latency. If the transfer bit rate of the file is lower than the network speed, the video can be played seamlessly. Therefore, when a user progressively downloads a high resolution / high definition video file from a server within a limited network bandwidth such as a wireless environment, frequent disconnection may occur.

In other words, since there are many limitations in the case of limited network bandwidth, such as a wireless communication environment, it is difficult to reuse existing multimedia contents without processing. Transcoding device is used as a reprocessing method to provide seamless multimedia service to users by minimizing such network traffic, but multimedia content such as MP4, skm, k3g, 3gp, and 3gp2 in the storage device in the server However, since metadata and media data are independently separated, there is a problem that progressive download cannot be implemented using a real-time transcoder.

The present invention was developed in order to achieve the above technical problem, the technical problem to be achieved by the present invention, the multimedia content stored in the storage device in the server as a multimedia content in which the metadata and media data are independently separated in real time The present invention provides a real-time transcoding device for progressive download of multimedia content in a file format in which metadata and media data are separated, which enables a progressive download using a transcoder.

In order to achieve the above technical problem, a real-time transcoding device for progressive downloading multimedia content in a file format in which metadata and media data are separated,

A real-time transcoding device installed on the server side to support progressive download of multimedia content in a file format in which metadata and media data are separated from a user terminal.

A metadata reprocessing unit for reprocessing the input metadata at a desired compression ratio;

A step 1 bit rate controller for providing correct metadata generation and a suitable bit rate between screens by using correlation between screens in the metadata reprocessing unit;

A decoding unit which receives screen data from the media data of the file format data in which the meta data and the media data are separated, and decodes some or all of the screen data;

An encoder which receives part or all of the decoded data from the decoder and encodes the codec into a desired codec; And

And a second stage bit rate controller which receives the target compression rate of the current screen from the first stage bit rate controller and provides an optimal bit rate through intra-correlation and encoding retry of the encoder.

In addition, the metadata reprocessing unit,

Metadata analysis unit that extracts the codec data descriptor (Element Stream Descriptor) by analyzing existing metadata for metadata reprocessing, and classifies screen information that needs to be reprocessed and information that does not require reprocessing to reduce execution time. ;

A screen information reprocessing unit for reprocessing the screen information at the bit rate suggested through the first step bit rate controller for the screen information requiring reprocessing; And

It is preferable that the metadata generation unit generates new metadata by combining non-reprocessed information, reprocessed screen information, and a data stream of a new codec inputted from an encoder.

In addition, the first step bit rate control unit,

A bit rate control setting unit which receives initial information from metadata before reprocessing and initializes a first-level bit rate controller;

From the initial information of the bit rate control unit, including the total number of screens, screen size, codec information, screen type, bit rate and frame rate, and sample information of metadata, the screen type for the current screen is determined and provides an appropriate compression ratio. A bit rate controller; And

A screen to be input by the second-level bit rate controller by storing the initial information of the bit rate controller including the total number of screens, screen size, codec information, screen type, bit rate and frame rate, and the screen type and compression rate of the bit rate controller between screens. It is preferable to include an information storage unit.

In addition, the bit rate controller between the screen,

A screen type predictor for predicting and determining a screen type only by sample information (synchronization sample information, DT (Composition Time) / CT (Composition Time)) input from metadata;

A maximum compression ratio predictor for predicting the maximum compression ratio of the current screen according to the screen type determined by the screen type predictor and an entropy encoding scheme in the codec of the transcoder encoder to generate correct metadata by preventing malfunction of two-step bit rate control;

A final compression ratio determiner for calculating a suitable final compression ratio based on the maximum compression ratio determined by the maximum compression ratio controller and the bit rate proposed by the screen bit rate controller per second;

A screen bit rate buffer control unit for preventing an overflow and underflow of the bit rate buffer per second generated according to the compression rate determined by the final compression rate determining unit; And

It is preferable that the average bit rate buffer control unit accumulates the screen bit rate per second generated by the screen bit rate control unit per second to prevent overflow and underflow of the entire bit rate and to stabilize the overall bit rate.

In addition, the two-step bit rate control unit,

A bit rate control setting unit which receives initial information (number of full screens, screen size, codec information, screen type, bit rate, and frame rate) from the screen information storage unit and initializes a two-level bit rate control unit;

A screen type determiner which finally determines a suitable screen type by using the setting value of the bit rate setting unit and the screen information determined by the screen type predictor of claim 4 in the decoder; And

It is preferable that the screen type determiner is configured with an on-screen bit rate controller that provides an appropriate bit rate for the current screen by inputting the screen type and the target compression ratio.

In addition, the on-screen bit rate control unit,

The decoder decodes the importance of the current macroblock in the picture using the pre-coding macroblock information including the macroblock type, the size of the motion vector, the coefficient, and the generated bit amount, and weights the bit rate to improve the picture quality. A macroblock analyzer;

A current screen bit rate predictor for accumulating the generated bit amount of the macroblock after transcoding from the encoder and predicting a bit rate to be generated in the current screen in consideration of the quantization level proposed by the next macroblock quantization level determiner;

Next macro for determining the quantization level of the next macroblock through verification between the current screen bit rate prediction unit by receiving the weight of the macroblock analyzer, the reference quantization level storage unit, and the average quantization level of the intra-screen average quantization level storage unit. A block quantization level determiner;

An on-screen average quantization level storage unit for accumulating / averaging the quantization level determined by the macroblock quantization level determination unit and reflecting it to the next macroblock to prevent a sudden change in image quality in the screen;

A re-encoding determination unit for determining whether to re-encode the bit rate predicted by the current screen bit rate prediction unit when it is not suitable for a target compression rate; And

Preferably, the recoding determination unit includes a reference quantization level storage unit for storing and adjusting the reference quantization level for the entire screen according to the re-encoding determination to prevent sudden image quality change and uncontrollable quantization level control in the screen. .

As described above, according to the present invention, MP4, skm, k3g, 3gp, and metadata, in which metadata and media data are independently separated as multimedia contents stored in a storage device within a server through two-step bit rate control between screens and in screens. Multimedia content in 3gp2 file format is encoded using a real-time transcoder to enable progressive download from the user's device. In addition, according to the present invention, by performing two-step bit rate control between screens and in screens during the stable metadata generation and transcoder execution, progressive download is possible in a real-time transcoder, and the execution time is reduced through effective bit rate control. Maximization of transmission efficiency and deterioration of image quality can be prevented.

1 is a block diagram illustrating a structure of a real-time transcoding apparatus for progressive downloading a multimedia content in a file format in which metadata and media data are separated according to an embodiment of the present invention;
FIG. 2 is a block diagram showing a detailed structure of the metadata reprocessing part of FIG. 1;
3 is a block diagram illustrating a detailed structure of a step 1 bit rate controller of FIG. 1;
4 is a block diagram illustrating a detailed structure of an inter-screen bit rate controller of FIG. 3;
5 is a block diagram showing a detailed structure of a two-step bit rate control unit of FIG.
FIG. 6 is a block diagram illustrating a detailed structure of an intra screen bit rate controller of FIG. 5; FIG.

 DETAILED DESCRIPTION In order to fully understand the present invention, the advantages of the operability of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings that illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, the server side transmits content suitable for the user's network environment through a real-time transcoder to provide a smooth service. The structure of the MP4, skm, k3g, 3gp, and 3gp2 file formats, unlike other file formats that contain header information per screen, includes metadata that contains all the playback information, including details of the content and the location and size of the file on the screen. It is composed of media data consisting of only video / audio data bundles. In the following embodiment, the multimedia content is described as an MP4 format by way of example.

As explained above, the structure of the MP4, skm, k3g, 3gp, and 3gp2 file formats, unlike other file formats that contain header information for each screen, contains all the playback information, including the details of the content and the location and size of the file on the screen. In order to progressively download the MP4 file format, which is separated into the existing metadata and media data consisting of purely video / audio data bundles, metadata transmission for video playback is preceded. The user device may complete the reception of the transmitted metadata and then play the video at the time of receiving the media data. This structure causes a problem in that when a transcoder is used, the server must first transmit metadata before performing real-time transcoding. In other words, metadata must be generated using a real-time transcoder without information on the screen before reprocessing. However, the generation and transmission of inappropriate metadata introduces screen degradation and unnecessary network waste in the user terminal and additional load on the server side. Therefore, there is a need to predict and generate optimal metadata in conjunction with a real-time transcoder before performing a real-time transcoder for MP4 progressive download.

To this end, the apparatus according to the invention performs a bit rate control over two stages. FIG. 1 is a block diagram illustrating a structure of a real-time transcoding apparatus for progressive downloading a multimedia content in a file format in which meta data and media data are separated according to a preferred embodiment of the present invention. 1, a real-time transcoding device according to the present invention,

A metadata reprocessing unit 20 for reprocessing the input metadata 100 at a desired compression ratio,

A first stage bit rate controller 22 for providing correct metadata generation and an appropriate bit rate between screens by using correlation between screens in the metadata reprocessing unit 20,

A decoding unit 24 which receives screen data from the media data of the MP4 file and decodes part or all of it;

An encoding unit 26 which receives a portion or all of the decoded from the decoding unit 24 and encodes it with a desired codec, and

The second stage bit rate controller 28 receives the target compression ratio of the current screen from the first stage bit rate controller 22 and provides an optimal bit rate through the intra-screen correlation and the encoding retry of the encoder.

The decoder 24 and the encoder 28 support heterogeneous transcoders and homogeneous transcoders, and cascaded by cascading the decoder 24 and the encoder 28 in a transcoder manner. Transcoder) and a hybrid transcoder using a combination of DCT spatial data and pixel spatial data are applicable. That is, the bit rate control apparatus of the present invention can be applied to various real-time transcoder requiring real-time MP4 progressive download.

FIG. 2 is a block diagram illustrating a detailed structure of the metadata reprocessing unit of FIG. 1. Referring to FIG. 2, the metadata reprocessing unit 20 is a device for reprocessing metadata to be transmitted at the same time as the start of the MP4 progressive download into metadata suitable for a desired bit rate. The information reprocessing unit 202 and the metadata generating unit 204 are configured.

The metadata analyzer 200 extracts the data descriptor of the codec in the MP4 file and inputs it to the decoder 26 in order to receive an element stream descriptor of the new codec of the encoder 24. do. In addition, the initial transmission delay time is reduced by reducing the execution time by separating the data related to the screen information and the data that is not reprocessed.

The screen information reprocessing unit 202 is reworked with the screen information corresponding to the target compression ratio in association with the first-level bit rate control unit 22.

The metadata generator 204 generates metadata to be transmitted by combining a data descriptor (Element Stream Descriptor) of the new codec inputted from the encoder 26, the reprocessed screen information, and the raw metadata.

FIG. 3 is a block diagram illustrating a detailed structure of the first stage bit rate controller of FIG. 1. Referring to FIG. 3, the first stage bit rate control unit 22 includes a bit rate control setting unit 220, an inter-screen bit rate control unit 222, and a screen information storage unit 224.

The bit rate control setting unit 220 receives basic information about the total number of screens, screen size, codec information, screen type, bit rate, and frame rate from the metadata analysis unit 200 among metadata reprocessing units. General initial information used for bit rate control is set and related information is stored in the screen information storage unit 224.

The screen information storage unit 224 stores all screen information of metadata reprocessed before the transcoder is executed, and the information is used for proper transcoding through two-step bit rate control during the transcoder.

That is, the first stage bit rate controller 22 receives the basic information about the total number of screens, screen size, codec information, screen type, bit rate and frame rate from the metadata in the bit rate control setting unit 220 and initializes the bit rate controller. The inter-bit rate controller 222 reprocesss the screen information by referring to the inter-screen correlation and the bit rate based on the actual input screen information and the target compression ratio, and the re-processed screen information is stored in the screen information storage unit 224. The second stage bit rate controller uses this to ensure accurate bit rate control. This one-stage bit rate control precedes bit rate control of metadata generation and transmission stages to support progressive download prior to real-time transcoder execution. The control is to calculate the optimal bit rate.

4 is a block diagram illustrating a detailed structure of the inter-bit rate controller of FIG. 3. Referring to FIG. 4, the inter-screen bit rate controller 222 determines a screen type predictor 2220, a maximum compression rate predictor 2222, a second screen bit rate controller 2226, an average bit rate buffer controller 2224, and a final compression rate. It is comprised by the part 2228.

The screen type predictor 2220 predicts or estimates the current screen type (I / P / B frame) using only metadata without using media data. Since information on the screen type is not specified in the actual metadata, additional media data analysis is required to know the correct screen type. However, analysis of media data causes transmission delays due to frequent memory accesses and many operations. In the present invention, the type of screen may be predicted using only synchronization sample information and DT (Composition Time) / CT (Composition Time) in the metadata without analyzing the media data. In addition, when a re-request comes from the final compression rate determiner 2228, the control unit may predict the next suitable screen type in addition to the previously determined screen type to provide more effective compression rate control.

The maximum compression ratio predictor 2222 calculates a maximum compression ratio of the current screen to determine whether to apply a given target compression ratio. This prevents malfunction of the metadata and unnecessary retries of the transcoder at an unsuitable compression ratio, and serves as reference information for calculating a suitable compression ratio in the final compression ratio determiner 2228. The maximum compression ratio may be calculated by considering the number of macroblocks of the current screen and the entropy encoding scheme of the applied codec, by applying a case in which no coefficients exist in the macroblock.

If an error occurs in the target compression rate per second due to the maximum compression rate limit or the change in the compression rate of the final compression rate determiner 2228, the screen bit rate buffer control unit 2226 approaches the target compression rate per second in consideration of the overflow and the underflow. To control the bit rate per second.

The average bit rate buffer control unit 2224 changes the screen bit rate per second, and when an error occurs in the overall target compression rate, the average bit rate buffer control unit 2224 accumulates a plurality of generated screen bit rates per second and generates the overflow and underflow that occur. In consideration of the overall target compression rate, the average bit rate is controlled to compensate for the overall picture quality.

The final compression ratio determiner 2228 considers the maximum compression ratio predicted by the maximum compression ratio predictor 2222 and the bit rates proposed by the screen bit rate buffer control unit 2226 and the average bit rate buffer control unit 2224 per second, thereby maintaining smooth image quality. In order to calculate the most suitable compression ratio. In addition, when the final compression ratio determiner 2228 determines that the determined final compression ratio has an effect on image quality degradation and a compression ratio error, the final compression ratio determiner 2222 controls the screen type predictor 2222 to predict a different screen type so as to provide a suitable final compression ratio for the current screen. Determine. This is again input to the screen bit rate buffer control unit 2226 per second to influence the final compression rate calculation of the next screen.

FIG. 5 is a block diagram illustrating a detailed structure of the second stage bit rate controller of FIG. 1. Referring to FIG. 5, the two-step bit rate control unit 28 includes a bit rate control setting unit 280, a screen type determination unit 282, and an in-screen bit rate control unit 284.

The bit rate control setting unit 280 receives the number of screens, the screen size, the codec information, the screen type, the bit rate, and the frame rate stored in the screen information storage unit 224 of the first-level bit rate controller 22 to control the second-level bit rate. It provides the target bit rate for the currently input screen by setting the initial information necessary for and linking with the transcoder.

The screen type determiner 282 performs two-step bit rate control based on the screen type predicted by the screen type predictor 2220 of the first-level bit rate controller 22 of FIG. 4 as an initial value, and the actual intra-screen compression rate and the target compression rate. If the screen type is changed due to this mismatch, the most suitable screen type among the decoded actual screen types and the candidate screen types is re-determined to approach the target compression ratio.

That is, the second stage bit rate controller 22 reads the screen information stored by the screen information storage unit 224 of the first stage bit rate controller 22 by the bit rate control setting unit 280 to initialize the bit rate controller, and determines the screen information. The unit 282 obtains and applies the current screen type from the bit rate control setting unit 280, resets the screen type suitable for retry, and the intra-bit rate control unit 284 determines the screen type and the screen in which the current transcoding is in progress. The bit rate control is performed in units of macroblocks by referring to the correlation and the bit rate of the information. The two-step bit rate control calculates the optimal bit rate by controlling the bit rate between macroblocks in the screen in consideration of the maximum compression size (bit rate) of the current screen determined in the first step bit rate control when performing a real-time transcoder.

FIG. 6 is a block diagram illustrating a detailed structure of the on-screen bit rate controller shown in FIG. 5. Referring to FIG. 6, the intra-screen bit rate controller 284 includes a macroblock analyzer 2840, a current-screen bit rate predictor 2842, a next macroblock quantization level determiner 2846, and an intra-screen average quantization level storage unit. 2844, a recoding determination unit 2848, and a basic quantization level storage unit 2849.

The macroblock analyzer 2840 analyzes the macroblock type, the motion vector size, the coefficient, and the generated bit amount of the currently decoded macroblock to calculate the weight of the current macroblock in the screen to determine the weight of the macroblocks to be used in encoding. Correct the picture quality.

The current picture bit rate predictor 2842 accumulates the bit amount of the encoded macroblocks, and predicts the current picture bit rate to be generated for the accumulated bit amount and the quantization level determined by the next macroblock quantization level determiner 2846. . If the predicted bit rate does not match the target compression rate, the recoding determiner 2848 controls the encoder 26 to perform recoding on the current screen.

Next, the macroblock quantization level determiner 2846 stores the weight of the macroblock analyzed by the decoder 24 and the average quantization level stored in the on-screen average quantization level storage 2844 and the reference quantization level storage 2849. With reference to the reference quantization level, a predicted quantization level for the next macroblock is presented, which is finally determined after conformance verification through the current picture bit rate prediction unit. Next, verify the suitability of the quantization level in the current picture bit rate prediction unit 2842 using the predicted quantization level suggested by the macroblock quantization level determiner 2846, and if not, adjusts the presented quantization level upward or downward. Repeat the conformity review until conformance. The final quantization level thus determined is input to the average quantization level in the screen and updated.

The recoding determiner 2848 determines recoding if the bit rate predicted by the current picture bit rate predictor 2842 is not suitable for the target compression rate. In detail, it prevents a malfunction of a terminal caused by a bit rate higher than a target compression rate and a decrease in transmission efficiency of a transmitter caused by a bit rate lower than a target compression rate.

The reference quantization level storage unit 2849 stores a quantization level that is a reference for the entire transcoder performance, and an initial value is determined by receiving an initial reference quantization level corresponding to the compression rate from the two-step bit rate control setting unit 280. If it is determined by the recoding determination unit 2848 to re-encode, the reference quantization level is adjusted up or down to provide the reference quantization level for the macroblock in the current picture to be recoded and the initial reference quantization level for the next picture. do. Such a reference quantization level minimizes the change in picture quality between screens and provides an appropriate initial quantization level in the picture, thereby reducing image quality deterioration due to an excessive adjustment of the quantization level to match the target compression ratio in the picture.

As described above, the apparatus according to the present invention reprocesses the metadata in the first-level bit rate control unit during reconstruction of the metadata of the real-time transcoder to progressively transmit multimedia content in a file format in which metadata and media data are separated. A suitable bit rate is provided, and the second stage bit rate control unit provides a suitable bit rate in the screen when the transcoder is executed.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

10: MP4
100: input metadata 102: media data
104: screen data
20: Metadata reprocessing department
200: metadata analysis unit 202: screen information reprocessing unit
204: metadata generating unit
22: 1-step bit rate control unit
220: bit rate control setting unit
222: bit rate control between screens
2220: screen type predictor 2222: maximum compression ratio predictor
2226: screen bit rate control per second
2224: average bit rate buffer control unit
2228: final compression rate determination unit
224: screen information storage unit
24: decoder
26: encoder
28: two-step bit rate control unit
280: bit rate control setting unit 282: screen type determination unit
284: bit rate control in the screen
2840: macroblock analysis unit
2842: current screen bit rate prediction unit
2846: next macroblock quantization level determiner
2848: On-screen average quantization level storage
2849: re-encoding decision unit

Claims (6)

In the real-time transcoding device installed on the server side to enable the progressive download of the multimedia content of the file format in which the metadata and media data is separated from the user terminal,
A metadata reprocessing unit for reprocessing the input metadata at a desired compression ratio;
A step 1 bit rate controller for providing correct metadata generation and an appropriate bit rate between screens by using correlation between screens in the metadata reprocessing unit;
A decoder which receives screen data from the media data of the file format data in which the meta data and the media data are separated, and decodes some or all of the screen data;
An encoder which receives part or all of the decoded data from the decoder and encodes the codec into a desired codec; And
And a second stage bit rate controller that receives the target compression rate of the current screen from the first stage bit rate controller and provides an optimal bit rate through intra-screen correlation and encoding retry of the encoder. Real-time transcoding device for progressive downloading multimedia content in separate file formats. The method of claim 1, wherein the metadata reprocessing unit,
Metadata analysis unit that extracts the codec data descriptor (Element Stream Descriptor) by analyzing existing metadata for metadata reprocessing, and classifies screen information that needs to be reprocessed and information that does not require reprocessing to reduce execution time. ,
A screen information reprocessing unit for reprocessing screen information at a bit rate suggested through the first-level bit rate controller for screen information requiring reprocessing; and
Meta data and media data are separated, comprising: a metadata generator for generating new metadata by combining non-reprocessed information, reprocessed screen information, and a new codec data descriptor (Element Stream Descriptor) input from the encoder. Real-time transcoding device for progressive download of multimedia content in file format. The method of claim 1, wherein the first step bit rate control unit,
A bit rate control setting unit which receives initial information from metadata before reprocessing and initializes a first-level bit rate controller;
A screen type for the current screen is determined from initial information of the bit rate controller (number of full screens, screen size, codec information, screen type, bit rate and frame rate) and sample information of metadata, and provides an appropriate compression ratio. A bit rate controller, and
Screen information that is input by the second-level bit rate controller by storing the initial information (number of full screens, screen size, codec information, screen type, bit rate and frame rate) of the bit rate controller and the screen type and compression ratio of the bit rate controller between screens. A real-time transcoding device for progressive downloading multimedia content in a file format in which metadata and media data are separated from each other. The bit rate controller of claim 3,
A screen type predictor for predicting and determining a screen type only with sample information inputted from metadata (synchronization sample information, DT (Decoding Time) / CT (Composition Time)),
A maximum compression ratio prediction unit for predicting the maximum compression ratio of the current screen according to the screen type determined by the screen type prediction unit and the entropy encoding scheme in the codec of the transcoder encoder, thereby generating correct metadata by preventing malfunction of two-step bit rate control;
A final compression ratio determination unit for calculating a final final compression ratio based on the maximum compression ratio determined by the maximum compression ratio controller and the bit rate proposed by the screen bit rate controller per second,
A screen bit rate buffer control unit per second for preventing an overflow and an underflow of the bit rate buffer caused by the compression rate determined by the final compression rate determining unit;
Meta data and media data are separated, comprising: an average bit rate buffer control unit for accumulating the screen bit rate per second generated by the screen bit rate control unit per second to prevent overflow and underflow of the entire bit rate and to stabilize the overall bit rate Real-time transcoding device for progressive download of multimedia content in file format. The method of claim 1, wherein the second step bit rate control unit
A bit rate control setting unit which receives initial information (number of full screens, screen size, codec information, screen type, bit rate and frame rate) from the screen information storage unit and initializes a two-level bit rate control unit;
A screen type determiner which finally determines a suitable screen type by using the setting value of the bit rate setting unit and the screen information determined by the screen type predictor of claim 4 in the decoder;
A multimedia content in a file format in which metadata and media data are separated, comprising: a screen bit rate controller configured to provide an appropriate bit rate for the current screen by inputting a screen type and a target compression ratio of the screen type determiner. Real-time transcoding device for sieve download. The method of claim 5, wherein the on-screen bit rate control unit,
The decoder decodes the importance of the current macroblock in the picture using the pre-coding macroblock information including the macroblock type, the size of the motion vector, the coefficient, and the generated bit amount, and weights the bit rate to improve the picture quality. Macroblock analysis unit,
A current screen bit rate predictor for accumulating the generated bit amount of the macroblock after transcoding from the encoder and predicting a bit rate to be generated in the current screen in consideration of the quantization level proposed by the next macroblock quantization level determiner;
Next macro for determining the quantization level of the next macroblock through verification between the current screen bit rate prediction unit by receiving the weight of the macroblock analyzer, the reference quantization level storage unit, and the average quantization level of the intra-screen average quantization level storage unit. Block quantization level determiner,
An on-screen average quantization level storage unit for accumulating / averaging the quantization level determined by the macroblock quantization level determination unit and reflecting it to the next macroblock to prevent a sudden change in image quality in the screen;
A re-encoding determination unit for determining whether to re-encode the bit rate predicted by the current screen bit rate prediction unit when it is not suitable for a target compression rate, and
And a reference quantization level storage unit configured to store and adjust the reference quantization level for the entire screen according to the re-encoding determination, to prevent a sudden change in image quality and control of excessive quantization levels in the screen. A real-time transcoding device for progressive downloading multimedia content in a file format in which metadata and media data are separated.

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